Reducing page faults in host OS following a live partition mobility event

Abstract

Page faults during partition migration from a source computing system to a destination computing system are reduced by assigning each page used by a process as being hot or cold according to their frequency of use by the process. During a live partition migration, the cold or coldest (least frequently used) pages are copied to the destination server first, followed copying the warmer (less frequently used) and concluded by copying the hottest (most frequently used) pages. After all dirtied pages have been refreshed, cutover from the instance on the source server to the destination server is made. By transferring the warm and hot pages last (or later) in the migration process, the number of dirtied pages is reduced, thereby reducing page faults subsequent to the cutover.

What is claimed is: 
     
       1. A method for reducing page faults during partition migration from a source computing system to a destination computing system comprising:
 designating in a computer readable tangible storage memory device a frequency of use designation for each of a plurality of memory pages being used by a first instance of a computer process currently being executed on a source computing system, wherein the source computing system has a microprocessor; 
 responsive to a live partition migration event beginning, rank ordering the plurality of memory pages according to the frequency of use designations to create a sequence of copying during the migration event, wherein the rank order of each partition can take the state of hot and cold coupled with a type of access designation of read-only and read-write; 
 copying read-write pages from the source computing system to a destination computing system according to a sequence of cold to hot; 
 copying read-only pages from the source computing system to the destination computing system according to a sequence of hot to cold; 
 refreshing one or more partition copies on the destination computing system in which any pages which have been dirtied on the source computing system since the beginning of the migration event; and 
 responsive to all pages being copied and refreshed as applicable, transferring execution of the first instance of the computer process to a second instance of the computer process executing on the destination computing system, and redirecting workflow from the source computing system to the destination computing system associated with the computer process. 
 
     
     
       2. The method as set forth in  claim 1  wherein the designation of frequency of use of each partition can further take a of warm, and wherein the copying sequence from hot pages to cold pages comprises copying warm pages after hot pages but before cold pages, and wherein the copying sequence from cold pages to warm pages comprises copying warm pages after cold pages but before warm pages. 
     
     
       3. The method as set forth in  claim 1  wherein the designations for frequency of use of each partition are periodically updated by a most-recently used page management daemon component of the computing system. 
     
     
       4. The method as set forth in  claim 1  further comprising, subsequent to the transferring of execution to the second instance of the computer process, releasing and reclaiming resources consumed by the copied partitions on the source computing system. 
     
     
       5. A computer program product for reducing page faults during partition migration from a source computing system to a destination computing system comprising:
 a computer-readable, tangible storage memory device which is not a propagating signal per se; and 
 one or more program instructions embodied by the computer-readable, tangible storage memory device for causing a processor to perform operations comprising:
 designating in a computer readable tangible storage memory device a frequency of use designation for each of a plurality of memory pages being used by a first instance of a computer process currently being executed on a source computing system, wherein the source computing system has a microprocessor; 
 responsive to a live partition migration event beginning, rank ordering the plurality of memory pages according to the frequency of use designations to create a sequence of copying during the migration event, wherein the rank order of each partition can take the state of hot and cold coupled with a type of access designation of read-only and read-write; 
 copying read-write pages from the source computing system to a destination computing system according to a scheduled order of cold to hot; 
 copying read-only pages from the source computing system to the destination computing system according to a scheduled order of hot to cold; 
 refreshing one or more partition copies on the destination computing system in which any pages which have been dirtied on the source computing system since the beginning of the migration event; and 
 responsive to all pages being copied and refreshed as applicable, transferring execution of the first instance of the computer process to a second instance of the computer process executing on the destination computing system, and redirecting workflow from the source computing system to the destination computing system associated with the computer process. 
 
 
     
     
       6. The computer program product as set forth in  claim 5  the designation of frequency of use of each partition can further take a state of warm, and wherein the copying sequence from hot pages to cold pages comprises copying warm pages after hot pages but before cold pages, and wherein the copying sequence from cold pages to warm pages comprises copying warm pages after cold pages but before warm pages. 
     
     
       7. The computer program product as set forth in  claim 5  wherein the designations for frequency of use of each partition are periodically updated by a most-recently used page management daemon component of the computing system. 
     
     
       8. The computer program product as set forth in  claim 5  wherein the program instructions further comprise program instructions for, subsequent to the transferring of execution to the second instance of the computer process, releasing and reclaiming resources consumed by copied partitions on the source computing system. 
     
     
       9. A system for reducing page faults during partition migration from a source computing system to a destination computing system comprising:
 a processor for performing a logical process under the control of program instructions; 
 a computer-readable, tangible storage memory device which is not a propagating signal per se; and 
 one or more program instructions embodied by the computer-readable, tangible storage memory device for causing a processor to perform operations comprising:
 designating in a computer readable tangible storage memory device a frequency of use designation for each of a plurality of memory pages being used by a first instance of a computer process currently being executed on a source computing system, wherein the source computing system has a microprocessor; 
 responsive to a live partition migration event beginning, rank ordering the plurality of memory pages according to the frequency of use designations to create a sequence of copying during the migration event, wherein the rank order of each partition can take the state of hot and cold coupled with a type of access designation of read-only and read-write; 
 copying read-write pages from the source computing system to a destination computing system according to a scheduled order of cold to hot; 
 copying read-only pages from the source computing system to the destination computing system according to a scheduled order of hot to cold; 
 refreshing one or more partition copies on the destination computing system in which any pages which have been dirtied on the source computing system since the beginning of the migration event; and 
 responsive to all pages being copied and refreshed as applicable, transferring execution of the first instance of the computer process to a second instance of the computer process executing on the destination computing system, and redirecting workflow from the source computing system to the destination computing system associated with the computer process. 
 
 
     
     
       10. The system as set forth in  claim 9  wherein the designation of frequency of use can further take a state of warm, and wherein the copying sequence from hot pages to cold pages comprises copying warm pages after hot pages but before cold pages, and wherein the copying sequence from cold pages to warm pages comprises copying warm pages after cold pages but before warm pages. 
     
     
       11. The system as set forth in  claim 9  wherein the designations for frequency of use of each partition are periodically updated by a most-recently used page management daemon component of the computing system. 
     
     
       12. The system as set forth in  claim 9  wherein the program instructions further comprise, subsequent to the transferring of execution to the second instance of the computer process, releasing and reclaiming resources consumed by the copied partitions on the source computing system.